That's the transformer inside the big gray box hanging just inside the front door. It takes the stupid "delta" power that PG&E feeds us and turns the useless 208v leg into 120v, from which we run all of the dimmer packs for the stage lighting.

Well, apparently it has been making burning electrical smells and is about to explode and kill us all, so it has to be replaced this week. That's $4,000 I didn't expect to be spending.

Now I'm just an unfrozen caveman, but I kinda think that any big steel box that costs four thousand fucking dollars should last more than ten years. Especially when it's a glorified wall wart! Geez.

I saw a transformer on a pole explode yesterday as I was walking into work. It sounded like a muffled shotgun blast and it rained down orange sparks that set the nearby bushes on fire. The power company had to come in and shut off the power for about 4 hours, which meant I needed to power down the office servers - because the city hasn't got its act together yet and reconnected the gas line to our backup generator from when they mistakenly capped the line last week. Great timing.

When I saw the first picture of the transformer, my first thought was to ask if maybe someone peed in it, because peeing in inappropriate places is practically a sport in SF. Then I saw how it's mounted high up near the ceiling, which would make that a major challenge.

It does seem like the trans should last more than 10 years.... I'll talk to our electrician here and see if he has any thoughts. :)

also X2 on the stupidass delta power. It causes more problems here at the shop then you'd imagine, espically when the machine tech doesn't know what he's doing and hooks up the 208V leg to leg of the machine that the control uses. Luckily just fried the 120=>24V DC transformer (just as in cost himself about 500 bucks), but still.

Actually, PGE's Open delta power provides 240V three phase, though in a half-assed sorta way. It sounds like this trans is stepping own the 208V leg of the open delta system to 120V, so DNA can have more power that they can actually use.

I read it as a high leg delta (closed delta with a center tap in one coil). Two of the phases to the center tap (neutral) give you the 120V, the third phase gives you the useless 208V. Phase-to-phase on all legs is 240V, so you can also use it as a 240V three phase (no neutral wire) as long as the 120V load is not large.

That's just a common (if outdated) setup and is consistent with what he wrote. Maybe PGE is providing something weird.

Wow, that was a lot of parentheses. Anyway, to clarify, that setup was very common in industrial areas where you mostly needed 240V three-phase, and just used a little bit of 120V for lighting and such. Times have changed, but as usual the infrastructure hasn't.

Yeah, that's exactly what we have at our shop (Berkeley) Our electrician called it an open-delta system, so that's what I thought. I'm no electrician, however. =P (I'm still confused how he's stepping down 3 phase power with only 2 transformers, for one of the machines.)

But yes, it's outdated and provides everyone involved a bit of hassle.

Anyway, JWZ, if you want I can talk to our electrician and see if he has any thoughts.

Well, you can have a high leg delta transformer that is also open by leaving out one of the non-center-tapped coils. It does seem magical, but it works the same as a regular high leg delta, giving you both 120V/208V single phase and 240V three phase, just with reduced power capability. Given that I only see two transformer coils in the photo, it's possible that Jaime has the same deal.